What can be added, except that it is a very very interesting and profesionnal course on the topic? I wonder the ability to concentrate thirty years of intense work in such a limpid document. Thanks so much for this. Unfortunatly one certainly needs exactly so many years to digest all the data exposed here if one is starting from the very beginning. This is demonstrating once more time that these discussions should be reserved to profis! A byside effect is that many many questionsions asked on PF on that topic become after that totally meaningless as long as the stuff has not been understood. My next winter time is already occupied.